Rubredoxin 1 Is Required for Formation of the Functional Photosystem II Core Complex in Arabidopsis thaliana.

Liping Che,Lin Zhang,Han Meng,Junxiang Ruan,Lianwei Peng

doi:10.3389/fpls.2022.824358

Abstract

Chloroplast thylakoid protein rubredoxin 1 (RBD1) in Chlamydomonas and its cyanobacterial homolog RubA contain a rubredoxin domain. These proteins have been proposed to participate in the assembly of photosystem II (PSII) at early stages. However, the effects of inactivation of RBD1 on PSII assembly in higher plants are largely unclear. Here, we characterized an Arabidopsis rbd1 mutant in detail. A drastic reduction of intact PSII complex but relatively higher levels of assembly intermediates including PSII RC, pre-CP47, and pre-CP43 were found in rbd1. Polysome association and ribosome profiling revealed that ribosome recruitment of psbA mRNA is specifically reduced. Consistently, in vivo protein pulse-chase labeling showed that the rate of D1/pD1 synthesis is significantly reduced in rbd1 compared with WT. Moreover, newly synthesized mature D1 and pD1/D2 can assemble into the PSII reaction center (RC) complex but further formation of larger PSII complexes is nearly totally blocked in rbd1. Our data imply that RBD1 is not only required for the formation of a functional PSII core complex during the early stages of PSII assembly but may also be involved in the translation of D1 in higher plants.

Highlights

Photosystem II (PSII) is the primary pigment-protein complex in the photosynthetic electron transport chain in oxygenic organisms
Our results show that the levels of the photosystem II (PSII) core subunits D1, D2, CP43, and CP47 are reduced to less than 1/8 of WT resulting in a drastic decrease of the various intact PSII complexes as well as PSII activity (Figures 1, 2)
Consistent with these results, pulse labeling and pulse-chase experiments showed that newly synthesized PSII core subunits are mainly present in the PSII reaction center (RC), pre-CP43, and pre-CP47 intermediates after labeling for 20 min and an additional 30-min chase (Figure 3B)

Summary

Introduction

Photosystem II (PSII) is the primary pigment-protein complex in the photosynthetic electron transport chain in oxygenic organisms. PSII harvests light energy to split water resulting in the release of oxygen and electrons that are transferred from water to plastoquinone in cyanobacteria, algae, and plants. PSII drives oxygenic photosynthesis together with PSI (Photosystem I), Cyt b6f (Cytochrome b6f ), and ATP synthase, and provides energy and oxygen for most living organisms on earth (Nelson and Junge, 2015; Shen, 2015). PSII RC is the minimum unit for the primary photochemical reaction and is composed of the subunits D1, D2, PsbI, and two subunits of cytochrome b559 (PsbE and PsbF) (Nelson and Yocum, 2006). CP43 and CP47 are peripheral core antenna subunits attached to the PSII RC.

Methods

Results

Conclusion